“Fragile element” in this instance means any physical element whose operation may be disrupted transiently or definitively by vibrations induced while the item of equipment of which it forms part is moved before being used. This could for example be a mirror of a space observation instrument, a module for measuring physical magnitude(s), a control module, an item of optical equipment, a plasma nozzle, a momentum wheel, a gyrometer or a gyroscope.
In certain fields, such as for example the space field, items of equipment are subjected at least transiently to more or less considerable movements and/or accelerations that cause their structure to vibrate and therefore certain elements that are coupled (or fixedly attached) thereto. This is notably the case with satellites that are placed in orbit by means of launchers or for certain items of equipment that are installed in the space shuttles.
When such an item of equipment comprises a fragile element, the latter must be “dimensioned” (or adapted) and/or coupled to damping devices, so as to withstand the load factors, if necessary during a launch phase.
This results in additional weight and/or space requirement, complexity and considerable development costs, and a possible deterioration of resolution in the case of elements using certain high-sensitivity mechanisms.
Furthermore, the damping device used is of the passive type, its effectiveness is limited, and when the damping device used is of the active type, it requires activation of an electric supply before the beginning of the mission, which is not usually allowed, notably in the space field.
Since no known damping device provides total satisfaction, the object of the invention is therefore to improve the situation.
For this purpose, it proposes a vibration-damping device for an item of equipment designed to be moved and comprising a structure to which at least a first element (deemed not to be fragile) and a second element that has to be protected from the vibrations because it is deemed fragile are coupled.
This vibration-damping device is characterized in that it comprises:                first piezoelectric transducer means inserted between the structure and the first element (and fixedly attached to the latter) and charged with converting the mechanical energy of vibration of the structure into electric energy,        at least one sensor coupled to the structure and charged with delivering measurement signals representative of the vibrations sustained by the item of equipment,        control means electrically supplied by the electric energy (delivered by the first transducer means) and charged with deducing from each measurement signal (delivered by a sensor) at least one amplitude of movement designed to compensate at least partially for the vibrations sustained by the structure, and to deliver control signals representative of each amplitude thus determined, and        second piezoelectric transducer means inserted between the structure and the second element (and fixedly attached to the latter) and charged with converting the control signals into movement(s) in order to damp at least partially for the second element the vibrations sustained by its item of equipment.        
Therefore, the damping device is of the active type while being self-sufficient with respect to its electric supply, due to the fact that it generates it.
The device according to the invention may comprise other features that may be taken separately or in combination and notably:                at least two sensors charged with delivering measurement signals representative of vibrations sustained by the structure in different directions, and second transducer means comprising at least two transducers charged with moving the second element in different directions;        each sensor may be charged with taking measurements of the accelerometric type;        its first transducer means may be made of a piezoelectric material chosen from piezoelectric monocrystals and piezoelectric ceramics;        its second transducer means and/or each sensor may be made of a piezoelectric material chosen from piezoelectric monocrystals and piezoelectric ceramics;                    its second transducer means and/or each sensor may be constituted of at least one stack of at least one layer of the piezoelectric material.                            each transducer (of the second transducer means) and the corresponding sensor may if necessary constitute together two complementary portions of one and the same stack of layers of said piezoelectric material.                                                when the item of equipment (or the second element) comprises means designed to mechanically damp the second element, and known damping capacities, the control means may be charged with deducing each amplitude of movement of each measurement signal taking account of the damping capacities;        its control means may be arranged so as to be activated and deactivated at chosen moments.        
The invention also proposes an item of equipment furnished with a vibration-damping device of the type explained above.
The invention is particularly well suited, although in a nonexclusive manner, to the space field and to the transport field, notably the rail transport field.
Still other objects and advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein the preferred embodiments of the invention are shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious aspects, all without departing from the invention. Accordingly, the drawings and description thereof are to be regarded as illustrative in nature, and not as restrictive.
The appended drawings can not only serve to supplement the invention, but also contribute to its definition, if need be.
The object of the invention is to allow at least the partial damping of a fragile element from the vibrations sustained by a moving item of equipment of which it forms part.
In the following, it is considered as a nonlimiting example that the item of equipment is an observation instrument fixedly attached at least partially to at least one satellite having to be placed in orbit by a rocket in order to fulfill a mission of space observation of the earth or a portion of the universe, from space.
But the invention is not limited to this type of equipment. Specifically it relates to any item of equipment, for space or otherwise, sustaining vibrations when it is moved and comprising a structure to which at least a first element considered not fragile and a second fragile element having to be protected from these vibrations are fixedly attached (or coupled). It may therefore involve, for example, a satellite, a land transport vehicle, such as for example an automobile or a truck or else an aircraft.